It has been known in the art to remove part of a resist to form an exposed area where a pattern is to be formed. The exposed area is subjected to plating process, and as the plating becomes higher than the height of the resist, it spreads over the resist. That portion of the plating which overlies the resist while exceeding the pattern width set in advance by the resist is called outgrowth. Such outgrowth is disclosed in Patent Document 1.
Meanwhile, a transfer process has been known in which a circuit board is fabricated by burying a pattern in an insulating base in order to smoothen the surface of the circuit board (see Patent Document 2, for example). The transfer process includes the step of joining the pattern of plating and an insulating resin together with pressure applied thereto.
However, where a circuit board is fabricated using the transfer process by joining a circuit board intermediate with an outgrowth and an insulating resin together with application of pressure, it is difficult to predict the electrical characteristics of the circuit board because the cross-sectional shape of the pattern plating is complex, with the result that the handleability of the circuit board lowers. In order to prevent the formation of an outgrowth, the height of the resist may be increased. In the case of forming a thick copper plating, however, it is often difficult to form a resist with a height matching the thick copper plating to be formed.